The roles of interleukin-1 and interleukin-1 receptor antagonist in antigen-specific immune responses.

Despite evidence that interleukin (IL)-1 promotes the proliferation of some T helper 2 (Th2) cell clones in vitro, the physiological role of IL-1 in the regulation of antigen-specific immune responses remains undefined. Using a liposome-DNA delivery system, we transiently expressed IL-1 receptor antagonist (IL-1Ra) to suppress IL-1 functions at the site of the antigen-specific primary immune response. Our data indicate, for the first time, that IL-1Ra downregulates antigen-specific IL-4 and IgE responses, with concomitant enhancement of interferon-gamma and IgG2a responses in vivo. In addition, IL-1 can promote Th2 development in an IL-4-independent manner in vitro. Thus, the balance between endogenous IL-1 and IL-1Ra during the primary immune response can be an important factor in determining the antigen-specific effector function of T cells.